1. Field of the Invention
The present invention relates to pain relief. In particular, the present invention relates to apparatus and methods for pain relief using ultrasound waves in combination with cryogenic energy.
2. Description of the Related Art
The use of ultrasound as a source of heat to treat pain is well known in the art. Heat generated by ultrasound is utilized to treat pain by either ablating the nociceptive nerve and nerve endings responding to the pain (for example U.S. Pat. No. 5,433,739 to Sluijter et al and U.S. Pat. No. 6,073,051 to Sharkey et al) or by warming the target tissue (for example U.S. Pat. No. 5,460,595 to Hall et al and U.S. Pat. No. 5,413,550 to Castel). The former method treats pain by permanently removing the body's ability to sense pain in the treated area. It has been suggested that damage to tissue surrounding the target tissue to be ablated by ultrasonic energy can be reduced by cooling the ultrasound electrode (U.S. Pat. No. 5,186,181 to Franconi et al). While removing the ability to sense to pain may provide short-term therapeutic benefits, it can cause long term harm by preventing the patient from detecting the development of new pathologies or the worsening of existing pathologies in the treated area. Unable to sense the pain associated with pathologic changes, the patient will delay seeking treatment thereby lowering the patient's prognosis.
Treating pain by heating the target tissue with ultrasonic energy has been proven effective. Assuming the therapeutic effects of ultrasound administration are tied to a thermal effect, these methods attempt to raise the temperature of the target tissue anywhere from 1 to 4 degree Celsius; deep pain and chronic pain are treated with higher temperatures (U.S. Pat. No. 5,413,550 to Castel). Heating target tissue, however, runs the risk of burning the patient or otherwise producing patient discomfort. Furthermore, studies investigating the therapeutic effects of ultrasound suggest that analgesic effects are not dependent upon the thermal effects of ultrasound. (Hsieh. Effects of ultrasound and diclofenac phonophoresis on inflammatory pain relief: suppression of inducible nitric oxide synthase in arthritic rats. Physical Therapy 2006; 86: 39-49; Young and Dyson. Effect of therapeutic ultrasound on the healing of full-thickness excised skin lesions. Ultrasonics 1990; 28: 175-180; Dino et al. The significance of membrane changes in the safe and effective use of therapeutic and diagnostic ultrasound. Physics in Medicine and Biology 1989; 34: 1543-1552.) Thus the use of ultrasound as an analgesic heat source is misguided and exposes the patient to unnecessary risks.
The use of cold temperatures to provide pain relief is also well-known. The most frequent use is the standard ice-pack that is used in everyday homes. The analgesic effect cool temperature provides stems from the cooling of neuronal tissue that causes the neuronal tissue to cease functioning. The use of cold temperatures for pain relief has evolved into a different format: cryogenics are now used to cool or freeze neuronal tissue such as nerves to produce an analgesic effect. The freezing of the tissue, however, provides a more dramatic effect than the simple cooling of neuronal tissue. Nerves are destroyed because the freezing of nerve cell bodies kills the cell body. For example, U.S. Pat. No. 6,761,715 to Carroll discloses a system and method for cooling or freezing neuronal tissue in order to induce lesions and produce cryoanalgesia. Additionally, U.S. Pat. No. 5,571,147 to Sluijter et al. discloses a general method of denervation of nerves to relieve back pain using both heating and cryogenic methods. While these methods may result in an analgesic effect, the drawback of these methods is that they result in the destruction of nerves. The present invention does not involve the destruction of tissues, cell, or nerves through heating, freezing, etc to provide pain relief.
U.S. Pat. Application No. 2002/0165529 to Danek discloses a system and method that utilizes cryogenic energy in combination with other sources of energy such as ultrasound or microwave to prevent collateral damage to the surface layer because of the high temperatures used. U.S. Pat. Application No. 2003/0014098 to Quijano et al. also uses cryogenic energy to protect peripheral tissue from applied thermal energy. The present invention does not us cryogenic energy to prevent collateral damage; the cryogenic energy used in the present invention is for an additional therapeutic purpose for pain relief.
Therefore, there is a need for a method and device that utilize both ultrasound energy and cryogenic energy in combination to provide effective pain relief that does not result in destruction of tissues, cells, or nerves.